[erlang-questions] Resisting "noconnection" / Remote termination of nodes

[Olivier BOUDEVILLE]

Hi,

For a more controlled overall termination of a distributed application, I 
try to shutdown synchronously a series of nodes, as properly and as in 
parallel as possible, in a non-OTP program. I imagine that using '[ 
rpc:cast( N, erlang, halt, [] ) || N <- MyTargetNodes ]' and then waiting 
for them to be terminated is the best approach for that.

As I want now these terminations to be synchronous (i.e. I want my 
terminate function to return only when all nodes are down for sure), I 
used to rely on checking their termination using net_adm:ping/1 (waiting 
for pong to become pang), but kept on getting (systematically) 
'noconnection' errors (exceptions?), which do not seem to be catchable (at 
least not with a 'try .. catch T:E ->.. end' clause). This happens as soon 
as there is at least one node (which happens to be on the same host - of 
course it is not the local node from which that rpc:cast is triggered) to 
halt.

I switched to looping on 'lists:member( Nodename, nodes() )' instead of 
ping (in both case with a proper waiting between checks), but I still get 
'noconnection' errors. It looks like 'noconnection' is VM-level? As 
expected, commenting-out the rpc:cast/3 never leads to 'noconnection'. 

I feel I would need something like net_kernel:unconnect_node/1.

My question now: how to deal gracefully with such a synchronous node 
shutdown and to resist to the (intended) loss of node(s)? 

Thanks in advance for any hint!
Best regards,

Olivier.
---------------------------
Olivier Boudeville

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